The present invention is directed to electrical converters, and especially to electrical converters that are small in size to facilitate their employment in products as a board mounted converter, or board mounted power supply device.
Many products today require multi-output power converters for their operation. In particular, dual output switched power converters are required that exhibit monotonic operation (i.e., the output voltage changes only in one direction) using a no-load start-up mode of operation and require regulated output or prebias characteristics under no-load conditions.
No-load start-up exhibiting monotonic operation has been achieved in the past by altering the feedback circuitry that monitors the output voltage and operates pulse width modulating circuitry to produce the desired output voltage. Such feedback circuitry modifications have been complex, bulky and expensive. The present invention is simple, compact, has a low part count (therefore having a lesser tendency to break down) and inherently insures that the converter device never starts with a no-load configuration.
Regulated output of a multi-output converter, such as a dual output converter, has been solved in the past by inserting a no-load resistance in the output circuitry of the converter. A problem with such an approach is that the no-load resistance is ever after in the output circuit of the converter during normal operation of the converter and therefore contributes to undesirable power consumption by the converter. This excess power consumption is usually manifested as unwanted heat. Prior art designers have included timer devices in the converter output circuitry to disconnect the no-load resistance from the converter output circuitry after a predetermined time. However, the timer circuitry employed in such prior art solutions has been bulky and complex. The complexity added cost and created an increased potential for break down to the products using those converter devices. Their bulkiness and complexity increased the difficulty of manufacturing a product employing such converters in compact, board mounted power supply devices.
The present invention provides a timed resistance in output circuitry of a converter for inclusion during no-load operation of the converter. The present invention is embodied in an apparatus having a low part count that uses power from an already existing power source within the converter devices with which it is intended to be used.
An apparatus for effecting a preload operation of an electrical converter device that includes a primary circuit section inductively coupled with at least one secondary circuit section presenting at least one output voltage at at least one output locus includes: (a) a load coupled with at least one selected output locus of the at least one output locus; (b) a switch device electrically coupling the load within the at least one secondary circuit section; and (c) a timer device coupled with the switch device. The timer device orients the switch device to electrically disconnect the load from the at least one secondary circuit section after a predetermined time interval elapses.
A method for effecting a controlled preload operation of an electrical converter device including a primary circuit section inductively coupled with a plurality of secondary circuit sections, each presenting an output voltage at a respective output locus, includes the steps of: (a) providing a respective load coupled with each respective output locus; (b) providing a respective switch device electrically coupling each respective load within a respective secondary circuit section; (c) providing a respective timer device coupled with each respective switch device; and (d) operating each respective timer device to orient the respective switch device to electrically disconnect the respective load from the respective secondary circuit section after a predetermined time interval elapses.
It is, therefore, an object of the present invention to provide an apparatus and method for effecting a preload operation of an electrical converter device that is compact in construction and efficient in operation.
Further objects and features of the present invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in which like elements are labeled using like reference numerals in the various figures, illustrating the preferred embodiments of the invention.